Lange Anna ("Tall Anna"), is a 47 metres (154 ft) high sea stack of Buntsandstein in the North Sea island of Helgoland, Germany. Its real local name is Nathurn Stak (Northern Stack). Climbing the stack is not allowed but tourists can look at the rock from a distance.
The stack is subject to severe weathering wear and decomposition. It was decided that any further effort for its conservation could do nothing but slowing down the process, so the Lange Anna today is consigned to its fate. Experts assume an acute danger of collapse of the top two thirds because of an instable layer of sands 16 metres above sea level, which already is the thinnest part of Lange Anna.
- Maren Lindstaedt, Thomas Kersten: Ein virtueller Klon für Helgolands Lange Anna durch terrestrisches Laserscanning. Archived 2007-06-10 at the Wayback Machine. In: Thomas Luhmann (Hrsg.): Photogrammetrie, Laserscanning, Optische 3D-Messtechnik – Beiträge der 4. Oldenburger 3D-Tage 2005. Wichmann-Verlag, Heidelberg, ISBN 978-3-87907-420-4, S. 216-223.
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